DD259715A1 - METHOD FOR PRODUCING VERGRABED HYDROGENIZED AMORPHIDE LAYERS - Google Patents

Abstract

The invention relates to a method for producing buried, by implantation masks laterally structurable hydrogenated amorphous layers with different depth and width in Si, AIII BV compounds and other semiconductors. These layers are used to convert light into electrical energy (solar cells), for storage circuits, in electrophotography, for the control of liquid crystal displays, as photodiodes and for image acquisition. The essence of the invention is that by means of a first implantation heavy ions are used to produce a buried amorphous layer and followed by a proton implantation for hydrogenation.

Description

For this purpose, see the page drawings

Field of application of the invention

Hydrogenated amorphous layers are used to convert light into electrical energy (solar cells), for integrated memory circuits, in electrophotography, for the control of liquid crystal displays, as photodiodes and for image acquisition (vidicon components).

The invention relates to a method by which buried, by implantation masks and laterally structurable hydrogenated amorphous layers can be produced with different depth and width, which extend the above applications in micro- and optoelectronics such that both compared to the monocrystalline material different electrical (Conductivity, trap density) and optical properties (absorption coefficient) new applications such as buried electrical interconnects, memory and control elements in discrete and integrated components as well as optical guide channels (waveguide) in integrated optoelectronic devices. An extension of the spectral sensitivity of solar cells and thus an increase in their efficiency must also be mentioned as a field of application.

Characteristic of the known state of the art

Hydrogenated amorphous layers are preferably prepared in or from Si by a suitable growth process that exploits synthesis of Si and atomic hydrogen, plasma enhanced processes, laser activated CVD processes, silane discharge, microwave assisted plasma, MOCVD processes, activated vaporization, and electron impact enhanced vapor deposition processes. (G.Winterling: "Amorphous Silicon [a-Si]" ·, Physics in our Time 16, 50 [1985]; "Properties of amorphous silicon", INSPEC, EMIS DATAREWIEWS Series No. 1, The Institute of Electronics Enginers 1985 ).

Also, the generation of amorphous layers by ion implantation is known, but hardly hydrogenated amorphous layers are produced under proton bombardment in silicon under room temperature conditions only at very high dose levels and in AmBy compounds.

Compared to the high level of production of hydrogenated amorphous silicon layers, the production of amorphous, hydrogenated layers in III-V compounds is not well controlled, although in GaAs and partially already in GaP hydrogen-bonded Aufampftechniken, including sputtering, Glowentladungen in CVD processes and plasma-assisted chemical transport processes are already partially used.

For the generation of buried amorphous, hydrogenated layers, there is still no reproducible process with simple technological process control, although partially recrystallized layers on amorphous zones can be produced by a non-conventional annealing, which, however, strongly influences the hydrogenation and is characterized by laterally difficult to define growth limits.

Further sources of literature for this presentation are:

Proc. Ninth Int. Conf. on "Amorphous and Liquid Semiconductors," Ed. B.K. Chakraverty and D. Kaplan, Journ. de Physique 42

(1981) Colloq. C-4, Suppl. No. 10 (1981)

Proc. Eleventh Int. Conf. on "Amorphous and Liquid Semicondustors," Ed. F. Evangelisti and J. Stuke, Journ. Non-Cryst

Object of the invention

The object of the invention is to provide a reproducible process with simple technological process control, which allows, in particular for AmBy compounds, a cost-effective production of buried hydrogenated amorphous layers.

Explanation of the essence of the invention

The object of the invention is to design a method for the preparation of hydrogenated amorphous buried layers in Si, A ||| B _V compounds, and other semiconductors, so that the targeted production regards depth and profile width is possible and also be substituted by the use of Implantation masks can be used to create a lateral fine structure in the depth. It should be avoided unwanted hydrogenation effects and complex formation with an electrical character.

According to the invention, the object is achieved in that a buried amorphous layer is produced in the material in a first implantation by means of heavy ions. This is preferably done with noble gas ions or with ions that make up the target material, with a dose of preferably DS ^ 10 ¹³ crrT ² . This is followed by a proton implantation with the same projected range for hydrogenation in the damage profile. The dose is preferably D> 10 ¹⁶ cm ~ ² only. In a further embodiment of the method, it is favorable to set the implantation temperature between 300 K and 700 K. As the implantation temperature increases, the ion dose required for amorphization increases (this difference is a factor of approximately 5 when the implantation temperature is increased from 300 K to 700 K). The required to achieve a certain degree of hydrogenation proton dose is almost independent of temperature, since at temperatures below 700K, the depth profile of the implanted hydrogen changes only weakly dependent on temperature.

The hydrogenated amorphous layer is produced under a nearly perfect surface layer by bombarding heavier ions and protons, preferably parallel to the lattice direction, whereby the degree of damage of the weaker damaged near - surface (less than 10%) is reduced by approx an order of magnitude is reduced (below 1%).

As a result of the injection into grid directions, the "buried" hydrogenated amorphous layer is generated in a "random" direction with respect to the bombardment in an approximately 50% greater depth. As a result of the associated profile spread, the required ion dose almost doubles.

The degree of damage of the less damaged near-surface layer is formed by annealing at T ~ 700K _at greatly reduced (by a factor of about 3 in the annealing at 700K with respect to the implantation at 300K). The "buried" hydrogenated amorphous layer remains largely intact.

The depth and width of the buried hydrogenated amorphous layer is controllable by the choice of ion energy and dose. In this case, it is advantageous for producing relatively thick layers to realize the layer by implantation with a continuous energy distribution in a specific energy interval.

The advantage of the method is that the depth and profile width of the buried hydrogenated amorphous layer can be largely controlled by the choice of energy and the Einschußrichtung and that implantation masks, which have archaeal character or may be metal masks, a lateral fine structuring in depth is possible , Preferably, in order to amorphize electrically in the crystal inactive ions (noble gas ions) or ionic ions (ions of a target component or like ions such as the target material (used to exclude unwanted hydrogenation effects and complexing with electrical character)

 The invention will be explained below using an exemplary embodiment.

Exemplary embodiment

By a heavy ion implantation in GaP, the ² was performed using Ar ⁺ ions with an energy of 24 MeV and a dose of D = 5 x 10 ¹⁵ cm ~ at 300 K under a Einschußwinkel of 30 ° to the surface, at a depth of 2, 3 to 3.3 pm produces an amorphous layer (see FIG. 1). As a result of the bombardment of ions, a defect concentration in the surface region up to a depth of 0.5 μm, which is below about 10% at the radiation damage maximum of about 2.8 / .mu.m, and is composed mainly of easily healable point defects.

This heavy ion implantation is followed by proton bombardment at a target temperature of 300 K, with the proton energy adjusted to the projected range of 2.8 m (0.35 MeV) and a dose of D = ^{3.times.10.sup.7 cm.sup.- 2} Layer has amorphous character and has a high degree of hydrogenation (Figure 2).

The effect of annealing on the radiation damage profiles and hydrogen distribution also becomes clear in FIGS. 1 and 2. It can be seen that the annealing at 700 K leads to a strong reduction of the degree of damage in the near-surface region, while the strong disruption of the buried layer is largely retained.

The depth profile of the hydrogen distribution detected by means of particle-induced γ-spectroscopy remains qualitatively stable in the temperature range 300-700 K and changes quantitatively in the maximum by about 30%.

pictures

Fig. 1: Depth profile of the radiation damage of GaP irradiated with 5 x 10 ¹⁵ cm " ² 24MeV Ar ⁺⁺ ions (α = 30 °) at 300K

was (o) and was healed at 700 K (o)

Fig. 2: Depth profile of the hydrogen distribution of GaP irradiated with 3 x 10 ¹⁷ cm " ² 0.3 MeV protons (α = 90 °) at 300 K (ο) and annealed at 700 K (ο).

Claims (5)

1. A process for the preparation of hydrogenated amorphous buried layers in Si, A ||| B _V compound and other semiconductors, characterized in that in the material by means of an ion implantation hochenergetischeh (M> 4), preferably with inert gas ions or with ions, from which the target material consists, at high dose, preferably with D> 10 ^l3 cm ~ ² , a buried amorphous area is generated and then by means of proton ^implantation with the same projected range and high dose, preferably with D> 10 ¹⁶ cm ~ ² , the Hydrogenation in the damage profile is made. 2. The method according to claim 1, characterized in that the implantation temperature is between 300 K and 700 K. 3. The method according to claim 1 and 2, characterized in that the bombardment with heavy ions (M> 4) and protons is carried out parallel to lattice directions. 4. The method according to claim 1 to 3, characterized in that the hydrogenation is followed by a heat treatment at temperatures around 700K. 5. The method according to claim 1 to 4, characterized in that relatively thick buried hydrogenated amorphous amorphous layers by implantation with a continuous energy distribution , generated in a given energy interval.